The present invention relates to icing of wind turbines. More particularly, the invention relates to ice detection for wind turbines and an ice detection unit. Specifically, the invention relates to a method for ice detection for a wind turbine, a method for calibrating an ice detection unit, and an ice detection unit for a wind turbine.
In the past, wind turbines experience an increasing demand. Therefore, more and more wind turbines are also planned and erected at sites with higher icing probability during the year. For example, such sites may be located in cold and hash climate like northern Europe, off-shore locations or alpine areas. These conditions lead to an increased probability of icing, i.e., ice accretion. Particularly, icing at the rotor blades of the turbines results in reduced energy output. This is based on increased mass loads on the wind turbine as well as in deterioration of the aerodynamic properties of the wind turbine. Further, regulations to shut down the wind turbine in the event ice-throw may occur further deteriorate the energy output.
Typically, the power output of the wind turbine decreases due to the icing. These and more details can be found, e.g., in “State-of-the-art of wind energy in cold climate” by T. Laakso, H. Holttinen, G. Ronsten, L. Tallhaug, R. Horbaty, I. Baring-Gould, A. Lacroix, E. Peltola, and B. Tammelin (April 2003), in “Betrieb von Windenergieanlagen unter Vereisungsbedingungen” by H. Seifert (Abstract from AUF WIND 99, ST. Pölten), in “Technical Requirements for Rotor Blades Operating in Cold Climate” by Henry Seifert, and in “arWind Energy Site Assessment in Harsh Climate Conditions” by B. Schaffner.